Hey it's not rocket science (as some would have you believe) first off it depends on the amount of carbonation you have in your beer, then what your pipe diameter is, and thirdly how long you are prepared to wait for that glass off goodness, be aware that commercialy we need to fill glasses as quickly as possible whilst retaining a decent head =$, you don't have that pressure (pun intended). Start with 2mtrs on your fizziest beer and if you get a glass of foam extend it to 3 mtrs or more (consider reducing the diameter of your pipes), if it takes forever then chop 500mm off and repeat, do not be surprised if you have a 1 mtr run or less for lightly carbonated ales and 2 mtrs ish for lagers/wheat beers etc. Balancing in a commercial enviornment is very different to what is required in a home keezer/whatever situation, decide what type of "beer" you're going to serve and the level of fizz you require then cut you line accordingly. Personally I use about 2 mtrs on everything except English ales (1 mtr and wait lol) better to wait a bit for the glass to fill than wait for the foam to subside, hope this helps. cheers G